When a watch is dismantled, the winding stem has to be removed before the movement can be taken out of the case. In general, it is necessary to press a pull-piece stud, which releases the various members of the stem mechanism from the actual stem.
When the watch is reassembled, the stem is reinserted, by pressing on the pull-piece stud again. However, the travel of the pull-piece stud is not generally blocked and it often occurs that the components of the stem mechanism leave their housing. In such case, the movement has to be removed from the case and dismantled for the stem mechanism to be able to be correctly assembled.
Further, the pull-out piece stud is generally close to the winding pinion, and there is consequently a risk of damaging the toothing with the tool used for removing the stem. In order to limit this risk, the tool entry point may be formed by an oblong hole or by a groove, which requires precise orientation of the tool, which is generally a screwdriver. If an unsuitable tool is used, the shaped hole is of no use. Further, the hole shape complicates and increases the cost of manufacturing the plate or bridge concerned, which would be simpler if a cylindrical hole were made.
Using a pull-out piece stud screwed into the pull-out piece results in an improvement. However, this pull-out piece stud does not actually limit the travel of the pull-out piece, since it has to be unscrewed to release the stem (instead being pressed as in ordinary mechanisms), and excessive unscrewing involves similar risks to the general case. This embodiment is also more expensive, because of the additional internal and external threads, and the fact of screwing in a component of very small size, which makes this embodiment difficult to use for small movements.
There is also known, from U.S. Pat. No. 1,087,525 in the name of BANNATYNE, a movement including connecting-pieces between the plate and the bridge, and wherein the shaft of the pull-out piece forms a connecting-piece in several parts, one of which carries a groove which holds the stamped pull-out piece, and is movable transversely with respect to the stem, to at least partially release the stem from a fork comprised in the pull-out piece in a plane perpendicular to the axis of the stem. This mechanism makes it possible to hold the components in the movement when the stem is dismantled, but is, however, expensive to manufacture, and requires significant space in the thickness of the movement.
CH Patent Application No 134409A in the name of SUTER & CIE UHRENFABRIK HAFIS discloses a winding and time-setting mechanism using a pull-out piece, wherein the pivot of the pull-out piece is formed by a stud that is movable along its axis within the frame of the movement, and disposed such that it is accessible from the rear face thereof, and can be actuated like a push-piece and pushed in with the pull-out piece comprised therein, against a return spring tending to ensure the assembly of the pull-out piece and the winding stem to each other.
CH Patent Application No 132861A in the name of MAMBRETTI MANLIO discloses a device for securing the time-setting pull-out piece, which includes a cylindrical stud, of which one end is screwed into the pull-out piece, and the other forms a head which projects several centimeters further than the barrel-bar to enable the winding stem to be removed simply by pressing on the head, the stud and pull-out piece being held in place by means of a plate forming a spring, which is secured to the main plate and abuts on the pull-out piece.